Heroes, Rogues, & Lovers: Testosterone and Behavior (25 page)

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Authors: James McBride Dabbs,Mary Godwin Dabbs

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BOOK: Heroes, Rogues, & Lovers: Testosterone and Behavior
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Testosterone is related to sexual activity, but the relationship is not a perfect straight line. Men within the normal range of testosterone, including those with low-normal levels, usually have satisfactory sex lives, as do many men whose testosterone levels fall below the normal range.
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Nevertheless, above-average levels of testosterone are generally correlated with above-average levels of sexual activity. I found that among the military veterans described in Chapter 4, those high in testosterone more often answered ''Yes" to the question "Have you ever had more than ten sex partners in one year?" The relationship holds true for women as well as men. High-testosterone women have sex more often than do low-testosterone women, and they have sex with more different people.
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This finding comes from a group of college students, and we think it applies to other women as well. For men and women who are high in testosterone, immoderation and variety are the spice of life. Low-testosterone people have sex less often, and with fewer different partners.
There have been proposals to use Depo-Provera, a synthetic form of the female hormone progesterone, to take away the testosterone of rapists, in what is called "chemical castration." European studies have shown that castration reduces crime, but these studies involved criminals who volunteered to be castrated, which makes them quite unusual.
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Ordinary prisoners might not show the same effect, but the topic is occasionally debated in state legislatures. When chemical castration works, it may do so by decreasing the general violence of an inmate more than by decreasing his interest in sex. In general, psychologists believe that rape has more to do with violence than with sex, although this view has come into question recently.
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People find creative ways to use the finding that lowering testosterone will lower sexual activity. An endocrinologist told me about a gay male couple in which both partners wanted their testosterone lowered so they would be less tempted to have sex with other men. Their request appeared to be within the limits of ethical medical practice, and their endocrinologist prescribed Depo-Provera. The men are now happy and content in their monogamous gay relationship.
What works with men also works with women; testosterone increases libido in both sexes. Testosterone as well as estrogen decreases in women after menopause, and a number of studies show that when a
 
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little testosterone is included in hormone replacement therapy, it increases positive mood and frequency of intercourse in postmenopausal women.
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A little is enough because women's bodies are sensitive to low doses of testosterone. I know women who take testosterone pills every day and swear by them.
These findings make it sound as if the effect goes only one way, with more testosterone producing more sex. Things are more complicated than that: Testosterone increases sex, and sex increases testosterone. Studies with male mice, rats, rabbits, and a bull named Jambo show that even the anticipation of sex increases testosterone. In a study of mice, the presence of a strange female caused the greatest increase in testosterone. In one famous study, a man who lived and worked alone in a lighthouse on an island shaved twice every day with an electric razor and weighed the trimmings from his beard.
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Every Friday he left the lighthouse and spent the weekend with his girlfriend. The trimmings from his razor showed that his beard grew more on Fridays, suggesting that his testosterone level was higher then. Anticipating romantic moments with his girlfriend affected his body, increased his testosterone, and put him in the mood for love.
Suzanne Bell and I studied the "lighthouse" effect further.
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She asked four couples to collect saliva samples after dinner and again around midnight every day for a week, and she asked the couples to indicate whether or not they had sex each evening. We found that salivary testosterone levels increased across the evening hours when there was sexual activity and decreased when there was no sexual activity. The results were similar for male and female subjects. Testosterone levels were not higher in the evening measures before sexual activity, suggesting no effect of anticipation. The subjects were established couples, however, for whom sex with each other had become a familiar pleasure. Because they had not spent a lonely week apart from each other, they might not have looked forward to sex with the same degree of anticipation as the man in the lighthouse did. Couples not so well acquainted with each other may be more aroused by anticipation and consequently more likely to have a testosterone increase. Suzanne and I considered a study in which we would measure testosterone in newly acquainted pairs, who, depending on how things go, may or may not be starting long-term relationships. However, we couldn't figure out the
 
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logistics of that kind of study. We didn't know where to find such couples or how to approach them about spitting for science. Another problem is that spitting in a vial might spoil the magic of a new romance.
Several years after we published our study, I had a call from a professor of pharmacology. He was trying to make sense of an unusual testosterone score. He had been talking with an Olympic-class athlete who failed a drug test, which indicated that the athlete had been taking testosterone. The athlete also called me and explained to me, as he had explained to the pharmacologist, that he had flunked the drug test right after returning from his honeymoon. He thought he had enjoyed sex on his honeymoon so frequently that his testosterone level had increased. I doubt that even a honeymooner's joyous excess could account for so big an increase, but the topic is worth another study.
Little is known about how testosterone affects sexual activity in very young or very old people. We do know that criminals often have early sexual activity in their backgrounds.
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When he was six years old, one future criminal told a shopkeeper he needed to a borrow a dollar for his parents. He took the dollar, and he and his five-year-old girlfriend disappeared. The parents became alarmed when they missed the children, and they found them two hours later. The boy had used his ill-gotten money to take his little girlfriend to a movie. Still, romantic impulses in children are not always a sign of high testosterone levels. An eight-year-old child in one of our studies made a pass at my student assistant, who was four times his age. At the end of their interview, he planted a most unchildlike long kiss on her cheek and asked her to be his girlfriend. That child turned out to be average in testosterone. Maybe aggressive behavior is a more reliable sign of high testosterone than are romantic gestures. Another child in the study, one who had kicked the teeth out of a six-year-old schoolmate, was high in testosterone.
The Seasons of Love
Testosterone varies with the seasons, and interest in love and sex varies more or less predictably along with it. Tennyson said, "In the spring, a young man's fancy lightly turns to thoughts of love."
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The large number of June weddings support his view, but there's more to the story. According to research data, testosterone levels are lowest in late spring
 
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and early summer.
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(There will be more about June and low testosterone later in this chapter.) According to the data, a young man's fancy should turn to thoughts of sex in late fall and early winter. That's when testosterone levels and sperm counts are highest.
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The peak time for human births in the Northern Hemisphere is around August or September, nine months after the high testosterone levels of the preceding fall. There is another, usually smaller, peak in the birthrate around March. March comes nine months after June, the traditional time for finishing school, getting married, and starting families. Many animals are seasonal breeders, but people are not. Nevertheless, there are some fairly regular trends in human birth statistics that become apparent when they are charted on graphs.
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The human birthrate is influenced by poetry, social customs, testosterone, and probably magic.
Most birds breed in the spring, and that's when they have high levels of testosterone. For birds, it makes evolutionary sense to find mates, build nests, and start families in the spring. When it's warm and when bugs, worms, and berries are plentiful, baby birds have the best chance for survival. Some animals, including rhesus monkeys, mate in the fall. That's when their testosterone is highest. Rhesus monkeys begin breeding every year in mid-October, come rain, shine, snow, or sleet, and their offspring are born in the spring. Many other animals have seasonal testosterone changes that correspond to changes in sexual activity. High testosterone and sexual activity go together in most snake species. There are two times a year when Arizona copperheads are high in testosterone and likely to mateonce in late winter when they come out of hibernation and once again in the spring. Snakes may mate only once a year, so they have to make the most of every sexual encounter. Each male has two penises, and each penis has a testis and a large duct in which to store semen. Almost as surprising, according to researchers who studied males in three species of rattlesnakes, male snakes have high levels of 17-
b
estradiol, a form of estrogen.
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Perhaps it was his elaborate sexual apparatus and his complicated mixture of male and female sex hormones that qualified the snake to bring sexual knowledge to Adam and Eve.
Seasonal hormonal variations were probably not as profound for Adam and Eve as for the snake and the other animals in the Garden of Eden, but people, too, are affected by the seasons. Research into sea-
 
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sonal affective disorder (SAD) shows that light has an effect on how our brains work.
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People who suffer from winter depression feel fine during the spring and summer. Sunshine, long days, and even bright artificial light are antidepressants for SAD victims. Other seasonal differences can affect us, too. A friend from Hawaii who spent a winter in New England said people were so bundled up there that they looked like Michelin tire advertisements. He lost interest in sex in New England, but when he returned to Hawaii, surrounded by flowering shrubs, sunshine, ocean breezes, and lightweight clothing, his interest in sex returned. I suspect his testosterone increased.
Many things influence human sexual behavior. One staple of the news business is how specific events, natural or technological, precipitate a rise or a fall in the birthrate exactly nine months later. There may be some truth to some of those stories, but when statistics are compiled on the basis of hindsight, who knows? It is not easy to predict when there will be a population surge in testosterone sufficient to raise the birthrate nine months later, or even when a particular person's testosterone level will rise. Every person has an average testosterone level, which is subject to small changes around that average. Greater or lesser interest in love and sex often parallels increases or decreases in testosterone.
Seasonal changes are one of the more or less predictable patterns in testosterone production. There are others. Testosterone is higher in the morning than in the evening, higher in youth than in old age, and higher in winning than in losing. In women, it is highest around the middle of the menstrual cycle. It is easy to understand menstrual cycle changes. Women ovulate at midcycle, when their testosterone levels are highest, making them most interested in sexual activity when they are fertile.
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During human evolution, women with this pattern of sexual activity would be more likely to conceive, have offspring, and pass the pattern on to future generations. It is harder to understand why there might be changes in testosterone across the day. Testosterone is highest in the morning for men and women, but sexual activity is more likely at night. Probably testosterone levels are high in the morning for the same reason that other hormone levels are high. When our ancestors woke up in the morning and went out to face a dangerous world, their systems needed to be on go, ready for action. When evening came it was time to
 
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rest, and testosterone dropped accordingly. These ancient patterns influence how we live today. Husbands and wives go to work in the morning when their testosterone levels are high, and then, when their work for the day is done, they have time for love.
Continual changes in testosterone level make the whole system flexible. Different levels support different actions, and all animals change with time. The deer in spring is not like the deer in fall, and people at twenty are not like people at sixty. Testosterone levels are higher when it is time to be dominant and lower when it is time to avoid fights. High testosterone in the breeding season is linked to both sex and fighting. Men are high in testosterone when they are competing for mates as adolescents and young adults. Women are high when they ovulate. Animals decline in testosterone outside the breeding season, females decline when they are not ovulating, and we all decline as we grow old. It would be risky for testosterone levels to stay high indefinitely. As discussed in Chapter 2, testosterone increases the chance of success in one-on-one encounters, but it also increases the risk of dying young. Testosterone is costly to the individual, and economy in its use is needed to minimize wear and tear on the body. When people and other animals are high in testosterone, they focus on sex and dominance and tend to ignore everything else. They neglect their health, eat too little, and misjudge such dangers as loaded guns, charging elk, or oncoming automobiles.
Testosterone and Marriage, like a Rhino (or a Peacock) and a Carriage
Let us consider how the sexual energy of testosterone might affect marriage and mate relationships, using rhinocerous and peacock analogies. Rhinos have one kind of machismo, and peacocks have another.
The rhinoceros is a hoofed animal with an odd number of toes, a member of the family that includes horse, donkey, wild Abyssinian ass, and extinct giant North American tapir. His territoriality, ferocity, and slow growth rate made him an unsuitable candidate for domestication. Scholars say that if it had been possible for Africans to domesticate the rhino as Eurasians had domesticated the horse, the history of the world might have been different.
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Rhinoceros-riding Africans might have

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